This application proposes to continue the Chicago Health and Aging Project (CHAP). The study currently has data for over 8,300 residents of a geographically defined, urban, biracial (black and white) community of the south side of Chicago, continues to enroll members of successive age cohorts of community residents as they become 65 years old, and uses magnetic resonance imaging (MRI) to identify sub-clinical brain infarcts and white matter hyperintensities (WMH). The study is currently of incident Alzheimer's disease, and the application proposes to broaden it to investigate risk factors for incident mild cognitive impairment (MCI). We hypothesize that risk factors for MCI, including race, APOE epsilon4, WMH detected on MRI, proneness to stress, use of HMG-CoA reductase inhibitors (statins) (inverse), and cognitive activities (inverse), are similar to those known or proposed for Alzheimer's disease. The study will provide data on the incidence and prevalence of MCI in the general population. We also propose to further identify risk factors for incident Alzheimer's disease, with emphasis on pursuing recent results suggesting that WMH seen on MRI may be a risk factor for Alzheimer's disease itself, that social and behavioral factors may influence risk of disease and that use of statins may be inversely related to risk of incident disease. Studies of both MCI and Alzheimer's disease will emphasize clarifying if blacks are at increased risk of disease as compared to whites and identifying the responsible factors. The study collects data in successive cycles and utilizes techniques permitting efficient combination of incident data across cycles for risk factor analyses.